CN108370182A - Claw rotor of a rotating electrical machine having claws with curved chamfers - Google Patents

Abstract

The invention mainly relates to a rotor of a rotating electrical machine of a motor vehicle, comprising at least one pole wheel (24, 25) comprising a plurality of claws (29), at least one claw (29) having at least one chamfered portion (57, 57') along an edge (51, 52) extending between a base and a free end (54) of the claw (29), the rotor being characterized in that the chamfered portion (57, 57') has a radial section in the shape of a circular arc.

Description

Claw rotor of a rotating electrical machine having claws with curved chamfers

technical field

The invention relates to a claw rotor of a rotating electrical machine having claws with chamfers in a curved form. The invention has a particularly advantageous, but not exclusive, application in the field of alternators and reversible electric machines for motor vehicles. Alternators convert mechanical energy into electrical energy. Reversible machines can also convert electrical energy into mechanical energy, especially for starting a vehicle's heat engine.

Background technique

In a known manner, the alternator described in document EP0762617 comprises a housing, and inside the housing a claw rotor rotating directly or indirectly with the shaft and a stator surrounding the rotor in the presence of an air gap. The pulley is fixed on the front end of the shaft.

The stator comprises a body in the form of a set of plates provided with notches equipped with notched insulators for fitting the windings of the stator. The windings comprise a plurality of phase windings which pass through recesses in the body and together with all the phase windings form a front and a rear bun on both sides of the stator body. The winding is obtained, for example, from a continuous wire covered with enamel or from a conductive element in the form of a rod, such as a pin in the form of a "U", the ends of which are connected to each other, for example by welding.

These phase windings are, for example, three-phase windings connected in star or delta form, the output of which is connected to at least one electronic rectifier module comprising rectifier elements such as diodes or transistors.

In addition, the rotor includes two magnetic wheels. Each wheel has a flange with a transverse orientation, on the periphery of which there are provided pawls, for example of trapezoidal form and axial orientation. The pawl of one wheel faces axially towards the flange of the other wheel. Each claw of a magnet wheel penetrates into the space existing between two adjacent claws of another magnet wheel, so that the claws of the magnet wheels overlap relative to each other in a tile-like manner. A cylindrical core is interposed axially between the flanges of the wheel. The core supports on its outer circumference a field winding wound in an insulator radially interposed between the core and the winding.

Motors of this type are known to emit acoustic noise caused by vibrations generated by the magnetic force present. In order to minimize this noise, it is known to provide a chamfer with a flat form on the edge of the claw, as described in document US5708318. However, this type of chamfer does not in some cases achieve the level of acoustic and electrical performance required by motor vehicle manufacturers.

Contents of the invention

The object of the present invention is therefore to improve the acoustic and electrical performance of the machine by proposing a rotor of a rotating electric machine of a motor vehicle, said rotor comprising at least one magnetic wheel comprising a plurality of claws, at least one claw Comprising at least one chamfer provided on an edge extending between the base and the free end of the jaw, the rotor is characterized in that the chamfer has a radial cross-section in the form of a circular arc. The radial section corresponds to the intersection between the claw and a plane perpendicular to the rotor axis.

Compared with a chamfered configuration with a straight cross-section, the invention thus makes it possible to obtain a smoother variation of the magnetic flux in the air gap, which makes it possible to improve the noise reduction performance while increasing the current delivered by the motor.

According to one embodiment, the ratio of the radius of curvature of the chamfer to the outer radius of the rotor is 0.5 to 0.9. This ratio is particularly advantageous in order to minimize the magnetic noise of the machine especially in the rotational speed range from 1800 to 4000 rpm.

According to one embodiment, the ratio between the distance between the center of the circle forming the outer circumference of the rotor and the center of the circle forming the curvature of the chamfer and the outer radius of said rotor is 0.1 to 0.5.

According to one embodiment, said chamfer is provided on the rear edge of the claw.

According to one embodiment, said chamfer is provided on the front edge of the claw.

According to one embodiment, the claw comprises a chamfer in the form of a circular arc arranged on the front edge and a chamfer in the form of a circular arc arranged on the rear edge.

According to one embodiment, the surface area of said chamfer decreases towards the free end of the corresponding claw.

According to one embodiment, said surface area of the chamfer is substantially zero at the free end of the jaw.

According to one embodiment, the claw has an outer radial surface and said chamfer is provided on said outer radial surface.

According to one embodiment, the chamfer extends axially between the base and the free end of the respective jaw.

According to one embodiment, said claws of said magnetic wheel are symmetrical.

According to one embodiment, said claws of said magnetic wheel are asymmetrical.

According to one embodiment, said rotor comprises interpole magnets, each positioned in a space separating two consecutive jaws.

According to one embodiment, the ratio of the maximum width of the chamfer to the pole pitch is 0.16 to 0.37.

The invention also relates to a rotating electric machine of the alternator or reversible machine type, characterized in that it comprises a rotor as defined above.

Description of drawings

The present invention may be better understood by reading the following description and by examining the accompanying drawings. These drawings are provided purely by way of illustration of the invention, and in no way limit the invention. In the attached picture:

Figure 1 is a schematic longitudinal section of an alternator according to the present invention;

Fig. 2 is a schematic diagram of the upper part of the claw provided with the magnetic wheel with double chamfers according to the present invention;

Figure 3 is a schematic view of the front part of the claw of the magnetic wheel according to the invention, showing the form of the arc of the chamfer;

4 is a graph showing two curves representing the noise level of an alternator according to the ratio of the radius of curvature of the chamfer to the outer radius of the rotor, each curve corresponding to a specific rotational speed of the alternator;

FIG. 5 shows a schematic variant embodiment of a rotor according to the invention with asymmetric claws.

Detailed ways

Identical, similar or analogous elements retain the same reference from one figure to another. In the description below, the "front" element is considered to be on the pulley side of the machine, and the "rear" element is on the opposite side.

FIG. 1 shows a compact polyphase alternator 10 , especially for use in motor vehicles. The alternator 10 converts mechanical energy to electrical energy and may be reversible. This type of reversible alternator 10 , known as an alternator-starter, makes it possible to convert electrical energy into mechanical energy, in particular for starting the vehicle's heat engine.

This alternator 10 comprises a housing 11 and inside the housing 11 a rotor 12 fitted with claws on a shaft 13 and a stator 16 surrounding the rotor 12 in the presence of an air gap 17 . The pulley 14 is fixed on the shaft 13 . This pulley 14 belongs to the means for transmitting movement by a belt between the alternator 10 and the heat engine of the motor vehicle. The axis X of the shaft 13 forms the axis of rotation of the rotor 12 and of the magnet wheels 24 , 25 .

The stator 16 comprises a body 19 in the form of a set of plates provided with notches, for example of the semi-closed type, equipped with notch insulators for fitting the phases of the stator 16 . Each phase comprises at least one winding which passes through a recess in the body 19 of the stator 16 and forms, with all phases, a front bun 20 and a rear bun 21 on both sides of the stator body 19 .

The windings are obtained, for example, from continuous wires covered with enamel or from conductive elements in the form of rods, such as pins connected to each other by welding. These windings are, for example, three-phase windings, which are connected in star or delta form, the output of which is connected to at least one rectifier bridge comprising rectifier elements, such as diodes or transistors of the MOSFET type, especially when the For example in the case of alternator-starters described in document FR2745445.

The rotor 12 comprises two magnet wheels 24 , 25 each having a flange 28 with transverse orientation provided on its outer circumference with claws 29 , for example of trapezoidal form and axial orientation. The pawl 29 of one wheel 24, 25 faces axially the flange 28 of the other wheel. Each claw 29 of a magnet wheel 24 , 25 penetrates into the space existing between two adjacent claws 29 of the other magnet wheel, so that the claws 29 of the magnet wheels 24 , 25 overlap relative to each other in a tile-like manner.

The outer circumference of the claws 29 together with the inner circumference of the body 19 of the stator 16 define the air gap 17 between the stator 16 and the rotor 12 . The inner circumference of the claw 29 is beveled so that the claw 29 is thinner on its free end side 54 .

A cylindrical core 30 is interposed axially between the flanges 28 of the wheels 24 , 25 . In this case, the core 30 is formed from two half-cores, each belonging to one of the flanges 28 . This core 30 supports on its outer periphery an exciting coil 31 wound in an insulator 32 radially interposed between the core 30 and the coil 31 .

In addition, the housing 11 includes a front bearing 35 and a rear bearing 36 assembled together. The bearings 35, 36 have a hollow form and each centrally supports a ball bearing 37, 38 for rotatably fitting the shaft 13 of the rotor. The rear bearing 36 supports a brush holder 40 provided with a brush 41 designed to rub against a ring 44 of a collector 45 connected to the field winding 31 by a wire connection. The brushes 41 are electrically connected to a voltage regulator fitted outside the machine.

The front bearing 35 and the rear bearing 36 include substantially lateral front openings 60 and rear openings 61 to allow passage of a fan 62 positioned on the front face of the rotor 12 and another fan positioned on the rear face of the rotor. The circulation of air generated by the rotation of 63 cools the alternator 10. Each fan 62 , 63 is provided with a plurality of blades 64 . The front lateral opening 60 and the rear lateral opening 61 are opposed to the front bun 20 and the rear bun 21 , respectively.

More specifically, as shown in FIG. 2 , each claw 29 having a trapezoidal form includes a front edge 51 which is first in contact with the air according to the direction of rotation of the rotor 12 indicated by the arrow SR and a rear edge 52 . 52 is located on the opposite side to the front edge 51 . These edges 51 , 52 extend between the base 53 of the jaw 29 , which partially coincides with the outer circumference of the corresponding flange 28 , and the free end 54 of the jaw 29 .

In this case, a first chamfer 57 is provided on the rear edge 52 of each claw 29 of the magnet wheel 24 , 25 . In this example, a second chamfer 57 ′ is provided on the front edge 51 of each jaw 29 of the magnet wheel 24 , 25 . Chamfers 57 , 57 ′ are provided on the outer radial surface 56 of the claw 29 . The chamfers 57, 57' extend axially between the base 53 and the free end 54 of the corresponding jaw 29, ie along the entire axial length of the jaw.

Preferably, the surface area of the chamfer 57 , 57 ′ having an overall triangular form decreases towards the free end 54 of the jaw 29 . The surface area of the chamfer 57 is substantially zero at the free end 54 of the jaw 29 .

As can be clearly seen in FIG. 3 , each chamfer 57 , 57 ′ has a radial cross-section in the form of a circular arc. The radial section corresponds to the intersection between the jaws 29 and a plane perpendicular to the axis X of the magnet wheels 24 , 25 . The invention thus makes it possible to obtain a smoother change in the magnetic flux in the air gap 17 compared to a straight chamfer configuration, so that the noise reduction performance can be improved while increasing the current output by the motor.

The ratio R1 is defined between the radius of curvature Ra of the chamfers 57, 57' and the outer radius Rr of the rotor 12, ie R1=Ra/Rr. The ratio R1 is preferably 0.5 to 0.9. As shown in FIG. 4 , this ratio is particularly advantageous for minimizing the magnetic noise of the motor in the rotational speed range of 1800 to 4000 rpm in particular (see curve A1 for a speed of 1800 rpm and curve A2 for a speed of 4000 rpm). It should be noted that the above operating speed ranges do not correspond to the minimum and maximum operating speeds of the alternator, but to a speed range for which there is a significant level of magnetic noise not covered by the aerodynamic noise of the fan must be attenuated.

In addition, a ratio R2 is defined between the distance EC and the outer radius Rr of the rotor 12, ie R2=EC/Rr. The ratio R2 is preferably 0.1 to 0.5. The distance EC is measured between the center C1 of the circle forming the outer circumference of the rotor 12 and the center C2 of the circle forming the curvature of the chamfer 57 .

A ratio R3 is also defined between the maximum width Chb_max of the chamfered portion 57 and the pole pitch Tp, ie R3=Chb_max/Tp. Tp is equal to the ratio between the inner circumference of the stator and the number of poles of the machine, ie Tp=πD/2p, where D is the inner diameter of the stator and p is the number of pole pairs of the machine. This ratio R3 is 0.16 to 0.37. The maximum width Chb_max is measured according to the circumferential direction on a plane parallel to the radial face of the flange 28 of the corresponding magnet wheel 24 , 25 .

As shown in the table below, this type of configuration makes it possible to reduce magnetic noise in an optimal manner and to increase the output current of the machine over the entire operating range of the rotor 12 .

In fact, a noise reduction greater than 5 dB is obtained with the bevel in the form of a circular arc for wider bevels (Chb_max = 7 mm) compared to the conventional straight bevel configuration. In addition, the output current enhancement of motors greater than 5A is obtained compared to conventional straight chamfer configurations.

Preferably, chamfers 57 are provided on the front edge 51 and the rear edge 52 of each jaw 29 . As a variant, the chamfers 57 , 57 ′ are provided only on the rear edge 52 or the front edge of the claw 29 . As a variant, only some of the jaws 29 of the magnet wheel comprise chamfers or double chamfers, the other jaws 29 have no chamfers.

In addition, the first chamfered portion 57 and the second chamfered portion 57' have the same radius of curvature Ra.

According to a variant, the radii of curvature associated with each of the chamfers 57 , 57 ′ are different from each other. For example, the claws 29 of one of the magnet wheels 24 may each have a first chamfer 57 associated with a first ratio R1 at low speed noise for the operating speed range. The lower aspect is optimal. The claws 29 of the other magnet wheel 25 may each have a second chamfer 57' associated with a second speed ratio R1' at a high speed for the operating speed range. The noise reduction aspect is the best. For example, for 1800 rpm, the ratio R1 is 0.7, and for 4000 rpm, the ratio R1' is 0.6. This type of construction makes it possible to minimize magnetic noise in an optimal manner over the entire operating range P of the rotor 12 .

In an embodiment, the claws 29 of the magnet wheels 24 , 25 are symmetrical, ie the midpoint M that can be seen in FIG. 2 passing through the center of the base 53 also passes through the free ends 54 of the claws 29 .

According to a variant, as shown in FIG. 5 , the jaws 29 of the magnetic wheels 24 , 25 are asymmetrical, that is, the midpoint M passing through the center of the base 53 of the jaw 29 is relative to the distance passing through the free end 54 of the corresponding jaw 29 . Parallel line offset. The asymmetric jaws 29 can be tilted in the direction of rotation SR (see arrow F1 ) or in a direction opposite to the direction of rotation SR (see arrow F2 ). As shown in Figure 5, the claws 29 of the two magnet wheels 24, 25 can be inclined in the same direction or in opposite directions.

As shown in FIGS. 2 and 5 , if applicable, the rotor 12 may include interpole magnets 46 each positioned within a space 66 separating two consecutive jaws 29 . The magnets 46 may be positioned inside all of the interpole spaces 66 , or only some of them, and may be regularly distributed around the circumference of the rotor 12 . The magnet 46 may be made of rare earth element NeFeB (Neodymium Iron Boron) or SmCo (Samarium Cobalt). The choice of material and the number of interpole magnets 46 make it possible to easily adapt the magnetic properties of the rotor 12 to the required power of the alternator.

It will be understood that the foregoing description is provided purely by way of example, without limiting the scope of the invention, and that any other equivalent substitution of different elements will not constitute a departure from the scope of the invention.

Claims (15)

1. A rotor (12) of a rotating electric machine of a motor vehicle, comprising at least one magnetic wheel (24, 25) comprising a plurality of claws (29), at least one claw (29) comprising a at least one chamfer (57, 57') on the edge (51, 52) extending between the free end (54) and the base (53) of said claw (29), The rotor (12) is characterized in that the chamfers (57, 57') have a radial section in the form of a circular arc. 2. The rotor according to claim 1, characterized in that the ratio of the radius of curvature (Ra) of the chamfer (57) to the outer radius (Rr) of the rotor (12) is 0.5 to 0.9. 3. The rotor according to claim 1 or 2, characterized in that the center (C1) of the circle forming the outer circumference of the rotor (12) and the curvature forming the chamfer (57, 57') The ratio between the distance (EC) between the centers of the circles (C2) and the outer radius of the rotor is 0.1 to 0.5. 4. The rotor according to any one of claims 1 to 3, characterized in that the chamfer (57, 57') is provided on the rear edge (52) of the claw (29). 5. A rotor according to any one of claims 1 to 3, characterized in that the chamfer (57, 57') is provided on the front edge (51) of the claw (29). 6. A rotor according to any one of claims 1 to 5, characterized in that the jaws (29) comprise a chamfer (57') in the form of a circular arc provided on the front edge (51) and a set A chamfer (57) in the form of a circular arc on the rear edge (52). 7. The rotor according to any one of claims 1 to 6, characterized in that the surface area of the chamfer (57, 57') decreases towards the free end (54) of the corresponding claw (29). Small. 8. A rotor according to claim 7, characterized in that said surface area of said chamfer (57, 57') is substantially zero at the free end (54) of said jaw (29). 9. A rotor according to any one of claims 1 to 8, characterized in that the claws (29) have an outer radial surface (56) and in that the chamfers (57, 57') Provided on said outer radial surface (56). 10. The rotor according to any one of claims 1 to 9, characterized in that the chamfer (57, 57') is at the base (53) and the free end of the corresponding claw (29) Extend axially between the portions (54). 11. A rotor according to any one of claims 1 to 10, characterized in that the claws (29) of the magnet wheels (24, 25) are symmetrical. 12. A rotor according to any one of claims 1 to 10, characterized in that the claws (29) of the magnet wheels (24, 25) are asymmetrical. 13. A rotor according to any one of claims 1 to 12, characterized in that it comprises interpole magnets (46), each positioned in the space separating two consecutive jaws (29) (66). 14. The rotor according to any one of claims 1 to 13, characterized in that the ratio of the maximum width (Chb_max) of the chamfer (57, 57') to the pole pitch (Tp) is 0.16 to 0.37 . 15. A rotating electric machine of the alternator or reversible machine type, characterized in that it comprises a rotor as defined in any one of the preceding claims.